Mechanical stress activated, or touch screen, interfaces are found in a variety of applications including computers, cell phones, ATM machines, and in automotive applications. These interfaces incorporate a variety of touch transducer sensors including resistive, capacitive, and optical technologies.
Many of the sensor technologies require power both for generating a signal and for powering electronics to sense or measure a change in the signal when a touch is applied to the interface. In order to reduce device power requirements, especially for small hand-held battery-operated devices, it would be useful to develop a mechanical stress activated interface that may require power for the sensing electronics, but may not require power to generate the sensed interface signal.
Piezo-optical materials are those that change their index of refraction under stress. Ambient light that passes through an unstressed piezo-optical core may be trapped within the core when its refractive index is altered by the application of stress. Therefore, a mechanical stress activated interface using piezo-optical materials can take advantage of ambient light including room lighting or light generated by a computer monitor to generate a sensing signal. In this way, a piezo-optical-based interface may require less power to generate an activation signal, than other touch screen interfaces.